1. Field of the Invention
The present invention relates to a compact printer adapted for use for example in an electronic table-top calculator.
2. Description of the Prior Art
Conventionally the typefont wheel for use in a compact printer is composed, as shown in FIGS. 1 and 2, of a typefont belt 2 of an elastic material having a desired number of types or symbols 1 and mounted on a cylindrical support 3. Said mounting is achieved by an adhesive material 4 or by fusion.
However such mounting method poses extreme difficulty in exact positioning of types 1, eventually leading to aberrated print positions.
As an example, in case of a typefont belt having thirteen types or symbols and wound around a cylindrical support 3, with dimensions of an outer diameter of 25 mm of the typefont belt; a character pitch of 5.2 mm and a character length of 2.6 mm, there will result, at the final type 5 as shown in FIG. 3, a positional aberration of 0.6 mm from the normal position A in case of a contraction of 50 microns in the character pitch. Thus, in case of printing on a paper 6, the characters appear as lacking approximately a quarter thereof, as shown in FIG. 4 (see numerals 1, 2, 3, 7 and 8).
Also where the typefont belt is fixed by means of the adhesive material 4 as shown in FIG. 2, the change in the character pitch may further be caused by the change in the thickness of the adhesive material.
Inversely in case of the typefont wheel shown in FIG. 3, an elongation of the character pitch by 50 microns will result in an entire elongation of 0.6 mm, forming a slack in the belt 2 as shown in FIG. 5 which causes stains on the print.
Particularly in case the typefont wheel is utilized in a printer of flying hammer type, an elevated precision is required for the typefont wheel in order to minimize other factors affecting the precision such as uneven rotation of the motor, fluctuation in the hammer flying type etc., but such requirement is extremely difficult to satisfy in the fixation with adhesive material or with fusion because of the difficulty in the assembly.